The skin is the largest organ in the human body, and at the same time an important barrier between the environment and the inside of our body. Dry room air can substantially reduce this protective function of the skin. If the humidity level is too low, the skin becomes chapped and cracked. Particles that can cause inflammation and dermatosis penetrate through cracks in the skin. Chronic skin complaints such as neurodermatitis or dandruff are aggravated by excessively dry air. Insufficient moisture makes itself felt in the form of uncomfortable tautness and itching of the skin, particularly on the forearms, elbows, hands, lower legs and feet. Especially in winter, when the humidity level drops with low temperatures, complaints about dry skin increase.
When does the skin dry out?
The first signs of excessively dry skin are thin scales and reddish patches. When moisture and fats (lipids) are lost, and there is nothing to make up for that loss, the skin starts to dry out. To prevent this, the skin is composed of three layers: The top layer is the multi-layered epidermis, including its protective horny layer. The skin’s barrier function serves not only to defend against unwanted foreign bodies from the outside, but also to ensure that too much fluid is not lost from the inside. The layers of skin below therefore provide the epidermis with a permanent supply of fluids. One of the prerequisites for this is drinking enough water. In addition, the lower layers of the skin also channel lipids upwards. Another protective layer of fat on the surface of the skin is provided by an oily mixture produced in the sebaceous glands.
Adequate humidity protects the skin
When the moisture and fat content of the skin layers decrease, the protective function is lost. The calloused skin becomes increasingly permeable, allowing particles and foreign substances to penetrate and cause skin irritation and inflammation. Dry room air can encourage this process. Particularly in winter, when heated air is dry, the environment draws more moisture from the skin. The moisture differential between the skin and the indoor space leads inevitably to increased loss of water. Transepidermal water loss (TEWL) is when moisture leaves the body through the epidermis by diffusion and evaporation. If this loss of moisture persists, the skin contracts like parchment, becomes scaled and cracked, and can become inflamed. Series of scientific tests show that below 50% relative humidity, there is a significant increase in transepidermal water loss. At the same time, this increase leads to a marked decrease in the hydrogenation of the skin. Studies confirm that even small increases in relative humidity, from 35% to 43%, result in very positive consequences for skin health and a reduction in any symptoms that occur.